Electrolytic condenser



AB T9T l 930. R. D. MERSHON ELECTROLYTIC CONDENSER Original Filed Dec.31, 1925 1e 23 Ii; 21 {T 14 (Java/atom. R ga/7.0. fife/she. 16- $5flame/1 Patented 1 9, 1930 mm: D. nmnsnorr, or new roux, n. Y.

nnncraomrrrc coimnusnn Application filed December 31, 1925, Serial 110.

This invention relates to electrolytic condensers, and its chief objectis to provide a condenser of good efli capacity in proportionmanufactured at low cost. To this and other ends the invention comprisesthe novel features and combinations hereinafter described.

ile the invention can be employed in various situations the advantagesabove mentioned make it especially useful in radio apparatus, as forexample as a smoothing condenser in devices for eliminating the ripplein rectified alternating current, and accordingly I have selected forillustration and specific description herein an embodiment designedparticularly for the purpose named. In this form it is easily possibleto construct a condenser of cylindrical shape not more than two and afourth inches in diameter and four inches in length, having a capacityof fifty microfarads. In the preferred form of the invention the anode,composed of aluminum or other metal capable of forming the necessarydielectric film on its surface, is a strip of sheet metal fastened toand wound spirally around a stiff rod of the same metal.

This rod may form the anode terminal. The

turns maybe spaced apart in any convenient and suitable manner, topermit circulation of the electrolyte, as for example by indenting thesheet metal to form numerous lugs on one side of the same. "As thusconstructed the anode is immersed in a suitable electrolyte, say anaqueous solution of borax and boric acid, in a cylindical vessel ofsuitable nonfilming metal, which may serve as the cathode.

The embodiment outlined above is illustrated in the accompanyingdrawing, in which Fig. 1 shows one end of the indented sheet metal stripbefore coiling.

Fig. 2 is a section on line 2,2 of Fig. 1.

Fig. 3 shows one end of the strip fastened 5 to the rod around which itis to be coiled.

Fig. 4 is a section on line 4-4 of Fig. 3.

Fig. 5 is aside view of the complete anode.

Fig. 6 is asection on line 66 of Fig. 5.

Fig. 7 is a detail section, on a larger scale,

on line 7 of Fig. 5.

money, and of lar e to size, WhlCh can e 78,534. Renewed .Tanuary10.1980.

Fig. 8 shows the complete condenser, partly in section.

The aluminum striplO, Fi 1, may be of.

any suitable thickness, .006 0 .an inch being satisfactory for acondenser of the size and capacity mentioned above. Along one edge, orboth if desired, are three rows of indentations parallel to the edge,forming three rows of small lugs or bosses 11. Those in the upper andouter row are on, or protrude from, one side of the strip and those inthe middle row are on the other side, Fig. 2. The rest of the strip maybe indented, in the same or in any other con venient pattern, but if thelugs are elongated, as shown at 12, for example, I prefer to make themin diagonal lines, as being less apt to cause the spiral turns of thestrip, in coiling it around the center stem or rod, to take polygonalcross section. I also prefer separated lugs rather than continuous ribs,as permitting freer flow of convention currents in the electrolyte. Inany case the lugs or, generally, the spacers, are preferably .as s arpas possible, and in some cases it may be advantageous to make theindentations in such manner as to actually perforate the metallaproducing sharp edges as indicated at 12,

strip is coiled the point of contact between the apex of the lug and theadjoining turn or convolution will have a very minute area,

as I have found that the smaller the area of contact the lessopportunity there is for corrosion at such points.

The aluminum rod 13 is split for a portion of its length to receive theend of the strip 10,'which is welded to the rod along its end edge. Thestrip is then coiled around the rod in spiral form, the lugs or spacersholding the turns apart to permit access of the electrolyte to all partsof the spiral anode thus formed and to allow free circulation of theelectrolyte. The three parallel rows of lugs or spacers at the upperedge interlock,

as it were, in the manner indicated in Fig. 7 and thus'serve to limitthe axial displacement of the turns. Otherwise a slight stress exertedaxially might distort the device into as clearly shown in 1g. 2, or 11,Fig. 7, so that when the v-rrrnjsn-res PATENT a pronounced conical form,as will be readily understood.

The container or tank for the electrol te and anod'e may be acylindrical vessel 14, B ig. 8, of suitable sheet metal. For economy ofspace the t 11k may be ust large enough to receive the anode and leaveroom for an insulating lining or other means to prevent electricalcontact between the anode and the tank. Otherwise it'rnay be desirableto wrap the anode with one or more turns of filming Wire (not shown) toprevent expansion of the spirally wound strip. A lining for the purposeindicated may consist of a bottom disk 15 of thin celluloid orcellophane and a strip 16 of like material bent to'cylindrical form andplaced loosely in the vessel. The vessel may be closed by a disk 17 ofinsulating material resting on a bead 18 on the inside near the top.Around the closure at the edge is a thin fiat ring or gasket of rubberor other suitable ma-' terial, and the edge of the vessel is crimped orturned in and down upon this gasket, forming a seal. A vent hole 19 isprovided in the cover 17. This can be plugged with Wax to preventspilling of the electrolyte in shipment and handling. When the condenseris put into service the wax can be perforated with a pin to permitescape of any gases resulting from electrolytic action in theelectrolyte. Or the usual disk of thin sheet rubber can be cemented overthe vent hole. When punctured with a pin the disk serves as an automaticvalve, opening when the pressure of the gas rises inside the tank andclosing as soon as the pressure is relieved. The tank is preferably deepenough, as in Fig. 8 for ex ample, where the dotted line 20 indicatesthe surface of the electrolyte, to ermit a substantial depth ofelectrolyte a ove the anode. The reserve thus provided takes care of theslow loss by electrolytic decomposition and in most cases makes itunnecessary to provide the vessel with a filling aperture and aremovable closure therefor.

The rod 13, threaded on its upper end, extends through the lid 17to'form the positive terminal and is clamped to the lid by nuts 21 setup firmly on yielding gaskets 22. The negative terminal may be a screw23 on a bracket 24 soldered to the can 14.

The electrolyte is preferably the one described in my Patent No.1,141,402, issued June 1, 1915, compounded in the following proportions:saturated borax solution (distilled water), two gallons; boric acid,three pounds; and an aditional half-pound of borax.

The necessary film can be formed on the anode in any suitable manner, asfor example by the methods described in my prior Patents Nos. 1,012,889of December 26, 1911, and 1,388,874 of August 30, 1921. Preferably thefilm is formed at such voltage as will peroperating voltage, say

mit the condenser to Withstand a substantial It is to be understood thatthe invention is not limited to the specific construction hereinillustrated and described but can be embodied in other forms Withoutdeparture from its spirit. Features not claimed herein are claimed in mycopending application Serial No. 249,314.

I claim- 1. An electrolytic condenser comprising a metallic vesseladapted to serve as the negative electrode, an electrolyte in thevcsseland in contact therewith, and a positive electrode comprising a centralstem or rod and a strip of filming sheet metal found spirally around thestem' with its turns spaced apart and provided with parallel rows ofinter-engaging lugs serving to prevent endwise displacement of the turnsof the spiral relative to each other.

2. An electrolytic condenser as described in the preceding claim, inwhich the vessel forming the negative electrode is provided with aninsulating lining and the spirally wound anode is free to expand againstthe lining.

3. In an electrolytic condenser, an electrode comprising a spirallycoiled strip of filming metal provided with a plurality of spaceddiagonal rows of spacing lugs to separate the convolutions of thespiral.

4. In an electrolytic condenser, an electrode comprising a spirallycoiled strip of filming metal provided with parallel rows of lugs onopposite sides of the strip to provide an interlock for limiting endwisedisplacement of the convolutions of the spiral.

5. In an electrolytic condenser, an electrode comprising a split rod offilming metal and a strip of filming sheet metal having one end insertedin the split in the rod and Welded thereto, said strip being coiledspirally around the rod and having inclined rows of lugs pressed out ofthe sheet to form spacing lugs and having a plurality of rows of similarlugs on opposite sides of the strip and parallel to an edge thereof toprovide an interlock for limiting axial displacement of the convolutionsof the spira v In testimony whereof I hereto aflix my signature.

RALPH 1). MERSHON.

